1. Field of the Invention
The present invention relates to an antenna apparatus.
2. Description of Related Art
In a base station of mobile communication such as a cellular phone or a PHS (Personal Handyphone System), since a service area is formed on a concentric circle whose center is the base station, an antenna apparatus with uniform directivity in the horizontal plane is used.
In general, in the antenna apparatus for the base station, it is desired that the antenna apparatus is made small in diameter and a construction for installing the antenna apparatus is made simple. An antenna element is desired which has a compact structure and enables the antenna apparatus to be made small in diameter.
A horizontal polarization antenna element (horizontal polarization omni element) shown in FIG. 20A and FIG. 20B is known to be used for an antenna apparatus (horizontal polarization omni antenna) in which the directivity of horizontal polarization in the horizontal plane is uniform.
In a horizontal polarization antenna element 200 shown in FIG. 20A, an arm portion (conductor portion) of a dipole antenna 201 horizontal to the ground is bent to form a compact structure.
A horizontal polarization antenna element 202 shown in FIG. 20B has a structure in which a patch antenna 203 bent in a rectangular shape is surrounded by parasitic elements 204. In the horizontal polarization antenna element 202, an electric wave radiated by the patch antenna 203 is shaped by the parasitic elements 204 and the directivity in the horizontal plane is uniformed.
When the horizontal polarization antenna element as shown in FIG. 20A or 20B and a vertical polarization antenna element having uniform directivity in the horizontal plane are arranged side by side and are disposed in an array shape, a polarization diversity omnidirectional antenna can be achieved.
An example of the related art includes JP-A-2010-62979.